1. Field of the Invention
The present invention relates to an apparatus and method for processing a substrate for use in the production of a semiconductor device (the apparatus for processing a substrate will be hereinafter occasionally referred to as xe2x80x9csubstrate-processing apparatusxe2x80x9d and the method for processing a substrate will be hereinafter occasionally referred to as xe2x80x9csubstrate-processing methodxe2x80x9d for simplification purpose). More particularly, the present invention relates to an improvement in the substrate-processing apparatus and substrate-processing method in which a substrate for a semiconductor device is wound in a roll form together with an interleaf before or after said substrate is treated. The substrate-processing apparatus includes a chemical vapor deposition (CVD) apparatus including a plasma CVD apparatus and the substrate-processing method includes a chemical vapor deposition (CVD) method including a plasma CVD method.
The present invention also relates to an apparatus and process for producing a photovoltaic element by way of CVD including plasma CVD.
2. Related Background Art
In recent years, various researches and developments have been conducted aiming at realization of sunlight power generation by means of a solar cell. In order to establish a definite situation for the sunlight power generation to meet the demand of electric power supply, it is required that solar cells having a sufficiently high photoelectric conversion efficiency and excelling in reliability are capable of being stably mass-produced and being always provided at a reasonable cost.
As such solar cell, public attention has been focused on an amorphous silicon (a-Si) solar cell (hereinafter referred to as xe2x80x9ca-Si solar cellxe2x80x9d), because the a-Si solar cell can be easily mass-produced at a reduced production cost and it can be stably provided at a reasonable cost, in comparison with a solar cell produced using a crystalline series silicon material or the like.
The reason for this is that the a-Si solar cell can be produced by using a raw material gas such as silane gas or the like which can be readily acquired at a reasonable cost and subjecting the raw material gas to glow discharge decomposition to form a functional deposited film such as a semiconductor film (or a semiconductor layer) or the like on a relatively inexpensive belt-like substrate (a substrate web) such as a metallic sheet or a resin sheet. And there have been proposed various film-forming method and apparatus for the production of an a-Si solar cell.
Incidentally, as such film-forming apparatus in order to form a functional deposited film as a semiconductor layer which is used in the production of a semiconductor device such as a solar cell, for instance, U.S. Pat. No. 4,400,409 (hereinafter referred to as document 1) discloses a plasma CVD continuous film-forming apparatus of a roll-to-roll system which can continuously form a functional deposited film as a semiconductor layer at a significant productivity. Document 1 describes that according to the plasma CVD continuous film-forming apparatus disclosed therein, it is possible to continuously form an element having a semiconductor junction by providing a long web member as a substrate on which a deposited film is to be formed and continuously moving in the longitudinal direction while passing said web member through a plurality of glow discharge regions to form a desired functional deposited film on said web member in each glow discharge region.
Besides, U.S. Pat. No. 4,485,125 (hereinafter referred to as document 2) discloses a method of continuously forming a deposited film on a long web member using a plasma CVD film-forming apparatus of a roll-to-roll system in which a substrate protective sheet is used such that said substrate protective sheet is laid on the surface of a deposited film formed on the web member. Document 2 describes that according to the film-forming method described therein, it is possible to continuously form a high quality deposited film on a long web member at good reproducibility and a high yield throughout from the beginning to the termination of the web member.
In addition, Japanese Unexamined Patent Publication No.82652/1997 (hereinafter referred to as document 3) discloses a method of forming a semiconductor film on a web substrate, including a step (a) of delivering a web substrate from a pay-out bobbin prior to forming a desired deposited film on said web substrate and a step (b) taking up said web substrate having said desired film formed thereon on e take-up bobbin through a steering roller while winding the web substrate winding on the take-up bobbin, wherein in said step (a) and said step (b), an interleaf comprising a resin, a chemical fiber or a glass wool is interposed between the web substrate and the steering roller in order to prevent occurrence of physical contact between the web substrate and the steering roller. Document 3 describes that according to the method described therein, shapes based on dusts or the like present on the back side of the web substrate are prevented from transferring onto the surface of the film formed on the web substrate and because of this, the surface of the film formed on the web substrate is prevented from being provided with irregularities.
However, the film-forming methods described in those documents have such subjects as will be described below, which are required to improve.
That is, for instance, in the case where the formation of a deposited film on a web substrate in accordance with the roll-to-roll film-forming manner is continuously conducted over a long period of time, in the step wherein the web substrate wound in a roll form on the bobbin together with the interleaf interposed in the roll form to cover the film-forming face of the web substrate is delivered from the bobbin and moved in the longitudinal direction for film formation while the interleaf being separately delivered and wound on the bobbin for the interleaf, when strong adhesion is present between the web substrate and the interleaf due to adhesion or electrostatic absorption of the interleaf, there is a fear such that the interleaf in pulled in the steering roller whereby the interleaf is sandwiched between the web substrate and the steering roller, where the interleaf is broken or the interleaf is in a state that the interleaf is mounted on the back face of the web substrate and it is moved into a first film-forming chamber adjacent to the substrate-delivering chamber together with the web substrate while maintaining said state.
Further, in the case where the rotation performance of a bobbin shaft for winding the interleaf fails due to aging of bearings for the bobbin shaft because of continuous repetition of the film formation over a long period of time and the winding speed of the interleaf becomes slower than the peeling speed of the interleaf from the web substrate, there is a fear such that the interleaf is gradually loosed and eventually, the interleaf is moved into a first film-forming chamber adjacent to the substrate-delivering chamber together with the web substrate while the interleaf being mounted on the back face of the web substrate.
When the interleaf is not normally wound, there is a tendency of causing problems such that abnormality is entailed for the transportation of the web substrate, and when the interleaf is taken into the first film-forming chamber as above described, depending upon the kind of the constituent of the interleaf, the interleaf is evaporated to deposit on the inner wall face or the like of the film-forming chamber or it is melted or burned in a worst case due to heat from the heater of the film-forming chamber, where the film-forming apparatus is greatly damaged.
Separately in the case where the web substrate having a plurality of deposited films sequentially formed thereon is wound on the bobbin, when the web substrate is wound on the bobbin together with a new interleaf while laying the interleaf on the film-forming surface of the web substrate so as to cover the film-forming surface and wherein the rotation performance of the bobbin shaft for delivering the interleaf fails and the speed for the interleaf to be delivered becomes faster than that for the web substrate to be wound on the bobbin, there is such a fear as will be described in the following. That is, the interleaf is gradually loosened and eventually, the interleaf is pulled in the steering roller in a state that the interleaf is mounted on the back face of the web substrate, where the interleaf is broken.
Without being noticed to the fact that the interleaf is broken during the film formation, when the film formation is continued, there is a tendency in that no interleaf is laid on the film-formed face of the web substrate which is wound after the time when the interleaf is broken. This situation is liable to entail a remarkable decrease in the yield of a film product and also in the characteristics thereof.
The occurrence of such problems as above described is limited only in the case of forming a deposited film on a web substrate by way of the roll-to-roll film-forming process. Similar problems are liable to occur also in the case of other substrate-processing apparatus in which a web substrate is treated by way of roll-to-roll manner. These substrate-processing apparatus include film-forming apparatus by means of sputtering, vapor deposition, CVD apparatus, plating, or coating, etching apparatus, and washing apparatus.
A principal object of the present invention is to eliminate the foregoing problems in the prior art and to provide an improved substrate-processing apparatus and method in which the foregoing troubles due to transport abnormality of the interleaf during the processing of a substrate (that is, the film formation on a substrate) which are found in the prior art are desirably eliminated.
Another object of the present invention is to provide a roll-to-roll film-forming apparatus and method which enable to efficiently form a high quality functional deposited film having satisfactory characteristics at an improved yield.
A further object of the present invention is to provide a roll-to-roll film-forming apparatus and method which enable to efficiently form a photovoltaic element including a solar cell having satisfactory characteristics.
A further object of the present invention is to provide a roll-to-roll substrate-processing apparatus comprising a substrate delivery chamber having a substrate delivery means having a web substrate (that is, a belt-like shaped long substrate) and an interleaf alternately wound and an interleaf takeup means which are provided therein, a substrate processing chamber (of a single- or multi-chambered system), and a substrate takeup chamber having a substrate takeup means and an interleaf delivery means having an interleaf wound thereon which are provided therein, wherein said substrate web and said interleaf are continuously delivered from said substrate delivery means where said interleaf delivered is continuously wound on said interleaf takeup means and said web substrate delivered is continuously transported into a substrate-processing chamber through a steering roller where said web substrate is subjected to desired processing, the web substrate processed in the substrate-processing chamber is continuously transported into said substrate takeup chamber where the web substrate is wound through a steering roller on said substrate takeup means together with an interleaf delivered from said interleaf delivery means such that the web substrate and the interleaf are alternately wound on the substrate takeup means, wherein said substrate-processing apparatus is provided with a mechanism to detect transport abnormality of the interleaf in the substrate delivery chamber or/and the substrate takeup chamber whereby preventing the interleaf from suffering adhesion to the web substrate and also preventing the interleaf from being taken into the substrate processing chamber together with the web substrate.
The term xe2x80x9cadhesionxe2x80x9d in the present invention indicates a state in that the interleaf and the substrate are contacted with each other. The present invention is aimed at detecting and preventing such contact (adhesion). Specifically, the present invention is aimed at preventing the interleaf from being transported in a state of being contacted (adhered) with the substrate.
According to the substrate-processing apparatus of the present invention, it is possible that a web substrate is continuously transported from the substrate delivery chamber into the substrate processing chamber while preventing the web substrate from being contacted with an interleaf which is delivered together with the web substrate where desired processing such as film formation is efficiently performed on the web substrate which is moving, and the substrate web thus processed in the substrate processing chamber is successively transported into the substrate takeup chamber where the web substrate is wound on the substrate takeup means while the processed surface of the web substrate being covered by an interleaf which is separately delivered without being contacted with the web substrate. Thus, there can be effectively obtained a rolled product comprising a web substrate having a processed surface (or having a deposited film formed thereon) and an interleaf which are alternately wound such that the processed surface (or the deposited film-bearing surface) of the web substrate is covered by the interleaf. This situation enables to efficiently and continuously form not only a high quality functional deposited film having satisfactory characteristics but also a high quality photovoltaic element (solar cell) having satisfactory characteristics on a web substrate at an improved yield.
The present invention also makes it an object to provide a substrate-processing method using the above substrate-processing apparatus.